Osteoporosis is mainly a major menopause-related public health problem in elderly women characterized by low bone mineral density (BMD). Peripheral blood monocytes (PBM) may act as precursors of bone resorption cells, osteoclasts, produce cytokins important for osteoclast differentiation, activation, and apoptosis, and represent major systemic target cells for sex hormones in bone metabolism. They play major roles in bone remodeling, turnover and thus menopause-related BMD change. Our hypothesis is that changes in the protein expression profiles in PBM may underlie mechanisms of BMD variation and be associated with menopause. Our major goals here are to identify proteins differentially expressed in PBM in females: 1) with high vs low BMD; 2) before and after menopause. This work will help to identify those proteins that are associated with osteoporosis and menopause in PBM. This novel line of work, together with our ongoing work in molecular genetic epidemiology and DMA microarray studies, will contribute significantly to identifying genes and their functional products as well as molecular markers for osteoporosis and those associated with menopause status in women. We will recruit 60 otherwise healthy Caucasian female subjects. In the age stratum 50-55, 30 with low and 30 high BMD (bottom or top 20% of age-matched population, i.e., Z-scores < -0.84 or > +0.84 at spine subjects will be recruited. Both groups have 15 pre- and 15 post- menopausal women. PBM from each subject will be isolated and sufficient total protein will be extracted and analyzed with both 2-dimensiona polyacrylamide gel electrophoresis (2-D PAGE) followed by mass spectrometry (MS) proteomics and 3-D nano liquid chromatography tandem mass spectrometry (3-D nano LC/MS/MS) approaches to test our hypothesis in order to identify proteins that are differentially expressed with regard to BMD variation and menopause. [unreadable] [unreadable] [unreadable]